Recently I pulled another computer out of a dumpster. The machine turned out to have some issues, but in the worst case it's still a source of some very useful parts. One of the issues is that the power supply (PS) fan stopped working, which has prevented me from debugging the other issues. Here's a brief summary of what happened:

PS is an Excalibur Retail XC-400B SATA ATX
main connector to mobo is 24-pin, BTX system design

At first, I'm certain the PS fan was working. At one point I swapped out the whole PS as part of my debugging. The same problems occurred with the other PS, so I figured the original PS was likely OK and cleaned it up a bit (removed dust). After I put it back in, the PS fan was not working and the PS overheated somewhat and began to smell a bit (which clued me in to the fan not working anymore).

I suspect the worst, it's just dead or at best intermittent, but I wanted to check if there could be something I'm missing. Is there any way the PS fan could be off due to some kind of configuration issue to do with the motherboard, BIOS, or anything like that?

Personally, I would recommend getting a decent PSU. I've seen a lot of mainboards, memory, and even videocards being blown out by a bad PSU. In almost all (if not all) the cases these were cheap 30$ PSU's.

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UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things.

If your fan is integrated with the power supply, you are typically out of luck.

The fan can be unscrewed from inside the PS (and I did that to clean it), but the wires are soldered to the PS board. I've not yet unsoldered them as I wanted to exhaust all other possibilites first (hence this thread). Hopefully I didn't break anything while cleaning it, but that might be a possibility.

I suspect #3), but need to investigate more. What I did do was apply 9V to the 12V fan at the solder points, and it didn't run. That doesn't seem conclusive though, since the PS could have been sucking the current. I'll have to unsolder 1 wire and try that again.

Quote:

Originally Posted by Carpetsmoker

Quite often (But not always!) PSU fans are just common 120x120mm 12v fans. You may need to solder the connector though.

Exactly, in this case.

About buying a new fan or PS, at the moment that's not being considered. Since the computer was free and has other issues, possibly serious, I'm not willing to put any money into it just to debug it. I did borrow a PS from another machine when I swapped the original one out, but it wasn't exactly the same (e.g., only 20-pin connector), so I don't really want to use it for further debugging since it might risk over-stressing it or something, leaving me with 0 extra computers rather than 2.

I found the problem, it was jggimi's #2). One of the fan wires had come off from inside the motor. The solder joint must have been physically weak, and broken when I was cleaning the fan.

So it needs to be soldered back on, but it isn't easy to get at the right spot. I managed to take the fan apart to a large extent, but the last step is difficult. The motor assembly seems to require being removed from the fan housing by spreading a C ring in tight quarters, and I don't have the tool to do it.

Anyway, the nature of the problem is now known and I can slowly ponder the options. Thanks again for the inputs.

Excellent idea!! Thank you for the creative thinking borne of experience I'm sure! I will try that, sounds like it could work.

Quote:

or.. buy a new power supply.

Well, just another fan would do (unless PS got worse from overheating).

Quote:

Originally Posted by Carpetsmoker

You can also use the 12V from one of the molex connectors. May be easier.

Those are the connectors on the mobo, right? Not sure how that would work. The problem is getting power to the fan because the wire disconnected inside (actually under) the fan motor assembly. So a connection needs to be made thereabouts, and BSDfan666's suggestion just might do it. I'm going to go try it right now. Will report back.

It was weird though. The only accessible points to solder on the motor assembly circuit board were the 4 legs of some little component that was mounted on top. It was one of those or nothing, so I used an ohm-meter to pick out the likely candidate, soldered the wire to it ... and it didn't work no-how. So, removed the wire, tried it without solder on the other 3 legs. There were some signs of life, but nothing consistent. Finally I tried the original leg again, and now it seemed to work well. . So I soldered it back on the same place again, put it together, a few drops of oil on the fan, and it all seems to work good now. Now I fixed what I broke and can get back to the other problems.

Good comments. I wouldn't have run it unattended, I was just hoping to debug the other problems. And yes it was my sole responsibility. Weird thing though the PS didn't have any warning sticker on it ... as I'd have expected it to.

But it's all a moot point now. Long story short: the next morning the fan worked briefly then died again, and that afternoon the PS gave up the ghost as well. So it's back to being a pile of spare parts again, unless/until I get hold of another PS. Useful parts though, 1G ram, 500GB drive almost new, and a DVD-RW (my first).

I had a PS fail with my wife's motherboard last December. No fan, no power. I went to my boneyard of parts (jggimi's used computer corral) and grabbed a second PS. The second PS worked for about 90 seconds, and failed.

Interesting, thanks. This might be the case here too, and adds to my resolve not to put any significant money into a new PS.

Quote:

Originally Posted by ephemera

i think the capacitors in a PS can potentially carry a deadly charge even after the PS is disconnected. it needs to be discharged before its safe to work on the PS. be careful!

You're certainly right about that, and I appreciate the concern! I did try to be careful, but evenso it's easy to slip up which makes this sort of thing not a really great idea. Fortunately no more plans to work on it as it seems a lost cause.

I should add, when I started this thread I knew working inside a PS was potentially dangerous, and I didn't want it to turn into some kind of tacit recommendation that people should do it. OTOH with all these new power saving features I wasn't sure exactly why a fan might be off, so I asked about it possibly being due to configuration. As the discussion evolved with everyone's kind help, well, it kind of went into the dangerous use of screwdrivers. So I'm glad people have brought up the dangers so future readers will have warnings about that. Either that or maybe the whole thread should be deleted, I wouldn't mind if moderators want to do that.